Spark Plugs?

[Desert Rat]

At 60 K miles, time to change plugs in my 98 LC (according to the manual).

Question: Auto Zone is asking $13.00 for DENSO Iridium plugs. Are these worth the added cost, verses, say, Autolite Double Platinum at $4.00?

And of course, do I really neeed to put in new plugs? I don't know for sure, but I suspect the plugs I have are the original Iridium.

Suggestions appreciated.

 

[chukiechz]

I put in the bosch double platinum, and it seems to have a little more grunt down low. But the top end pull seems a bit sluggish. That could just be the LX though since it has so many miles

 

[CPJONES1231]

you shouldnt have to change them until 90k with the Iridium plugs.

 

[ShottsUZJ100]

Iridiums in my 2001 were replaced voluntarily by me at 90K. The manual calls for 120K replacement. I try to do things early. I re-bought the factory plugs.

 

[Jukelemon]

Yeah, 60k is pretty early-actually it is real early.

I would wait

 

[marques]

One day, around 65k miles, out of the blue, my truck would not start one morning. No matter how long I cranked it or hit the gas it wasn't doing even a hint of starting. Just for the heck of it I decided to put new plugs on it. All they had at Autozone was regular Bosch Super plugs. Cheap also: about $10 for all 8. Anyway, I put new plugs in, it was a little hard to start (apparently it was a little flooded), but that fixed it. I got new iridium plugs the next day for about $10 ea, but have been putting it off because the truck has been running just great with the regular Bosch plugs. Maybe I'll finaly put them in one of these days, now that the Bosch Super plugs have about 20k miles.

The factory Iridium plugs I pulled did not look very good at all. The ceramic even had some hairline cracks on a few plugs. I would not feel comfortable at all running them for more than 60k miles, neve mind 120k!

Something else I learned was that these trucks have an electronic throttle. Yes, there is a mechanical cable from the accelerator to the throttle, but unless the electronics do their magic, the throttle only opens a little bit when you have the accelerator completely floored. Meaning that if you are trying to start a slightly flooded engine, you may have to put the pedal to the metal for the throttle to open maybe 15%... otherwise it just stays closed.

 

[Jukelemon]

Not to question what happened to you, but an efi engine is very very difficult to flood considering exactly what you just stated above. As well, pushing the pedal down when trying to start is not the way you start an efi engine.

I bet it was something else and not the plugs-it would also be very very rare that every plug at the same time went bad.

 

[Cruiser4UGA]

I changed my plugs at 60k and they were nasty. I could easiliy see scorching and blow by on the ceramic. The plugs were covered in deposits as well. I also think that if it would have waited much longer I could not have gotten them out either. Being in the car for 7 years and 60k the plugs were basically seized in there. When I put the new ones in I highly would recommend anti seize. I noted that one of my cylinders was running very very lean when I looked into it, and I was having a problem with high RPM power. (passing) I took out the injector and it was also clogged up really bad on my flow meter. A nice injector service by myself, and new plugs and I could no longer "feel" it running, my gas mileage went up by 1.1 mpg average and I have plenty of high rpm power.

In other news, I just got it back from the shop yesterday. Did the whole timing belt service waterpump, etc, just about everything that could be done to the thing. I also did the road force balancing, my interstate driving vibration is gone! Yeah! No more shaking steering wheel.

 

[Landpimp]

check with Cdan on the price on the ND plugs, pretty sure my parts guy said they were much cheap then that, like $60 for the set of 8

I would NOT run the Autolites.........

At 60 K miles, time to change plugs in my 98 LC (according to the manual).

Question: Auto Zone is asking $13.00 for DENSO Iridium plugs. Are these worth the added cost, verses, say, Autolite Double Platinum at $4.00?

And of course, do I really neeed to put in new plugs? I don't know for sure, but I suspect the plugs I have are the original Iridium.

Suggestions appreciated.

 

[marques]

I believe I flodded it by trying to repeatedly start it with the bad spark plugs. I'm sure the fact the the throttle wasn't opening didn't help either (you need air to mix with the fuel). The computed dumps lots of fuel in there when you are cranking the engine...

The fact remains my stock Iridium plugs looked really bad after "only" 65k miles and I would personally not run them for more than 60k miles.

 

[Jukelemon]

Marques:

Not to beat a dead horse, but you will have to get me some data on the efi system you are referencing in terms of "dumping a lot of fuel during initial start up". Typical fuel systems do not dump any more fuel during start up. What they do is regulate air flow through choke systems. Someone jump in if this is not the case with our 4.7's. My point is that it is very rare for a plug to get so fouled that it will not start an engine. My LC has 122k miles with the original plugs. I have 0 issues with acceleration/starting. But maybe I have the exception?

 

[DMX84]

Leave the Autolites in the Ford products.
I’ve started using an ND iridium plug in my Trials bike, works well. The electrode is very tiny, but won’t erode away like a normal plug, thus changing the gap.
I have a spark plug cleaner that you just put it in and sand blast the plug, maybe this is what needs to be done periodically on the LC’s?
Dean